•Simulated hydrographs show strong sensitivity to precipitation inputs.•Runoff errors were reduced by 36.9% for calibrated model with WRF data assimilation.•Transferability of model parameters to ...ungauged basins is found appropriate.
A fully-distributed, multi-physics, multi-scale hydrologic and hydraulic modeling system, WRF-Hydro, is used to assess the potential for skillful flood forecasting based on precipitation inputs derived from the Weather Research and Forecasting (WRF) model and the EUMETSAT Multi-sensor Precipitation Estimates (MPEs). Similar to past studies it was found that WRF model precipitation forecast errors related to model initial conditions are reduced when the three dimensional atmospheric data assimilation (3DVAR) scheme in the WRF model simulations is used. A comparative evaluation of the impact of MPE versus WRF precipitation estimates, both with and without data assimilation, in driving WRF-Hydro simulated streamflow is then made. The ten rainfall–runoff events that occurred in the Black Sea Region were used for testing and evaluation. With the availability of streamflow data across rainfall–runoff events, the calibration is only performed on the Bartin sub-basin using two events and the calibrated parameters are then transferred to other neighboring three ungauged sub-basins in the study area. The rest of the events from all sub-basins are then used to evaluate the performance of the WRF-Hydro system with the calibrated parameters. Following model calibration, the WRF-Hydro system was capable of skillfully reproducing observed flood hydrographs in terms of the volume of the runoff produced and the overall shape of the hydrograph. Streamflow simulation skill was significantly improved for those WRF model simulations where storm precipitation was accurately depicted with respect to timing, location and amount. Accurate streamflow simulations were more evident in WRF model simulations where the 3DVAR scheme was used compared to when it was not used. Because of substantial dry bias feature of MPE, as compared with surface rain gauges, streamflow derived using this precipitation product is in general very poor. Overall, root mean squared errors for runoff were reduced by 22.2% when hydrological model calibration is performed with WRF precipitation. Errors were reduced by 36.9% (above uncalibrated model performance) when both WRF model data assimilation and hydrological model calibration was utilized. Our results also indicated that when assimilated precipitation and model calibration is performed jointly, the calibrated parameters at the gauged sites could be transferred to ungauged neighboring basins where WRF-Hydro reduced mean root mean squared error from 8.31m3/s to 6.51m3/s.
The city of Genoa, which places between the Tyrrhenian Sea and the Apennine mountains (Liguria, Italy) was rocked by severe flash floods on the 4th of November, 2011. Nearly 500mm of rain, a third of ...the average annual rainfall, fell in six hours. Six people perished and millions of Euros in damages occurred. The synoptic-scale meteorological system moved across the Atlantic Ocean and into the Mediterranean generating floods that killed 5 people in Southern France, before moving over the Ligurian Sea and Genoa producing the extreme event studied here.
Cloud-permitting simulations (1km) of the finger-like convective system responsible for the torrential event over Genoa have been performed using Advanced Research Weather and Forecasting Model (ARW-WRF, version 3.3).
Two different microphysics (WSM6 and Thompson) as well as three different convection closures (explicit, Kain–Fritsch, and Betts–Miller–Janjic) were evaluated to gain a deeper understanding of the physical processes underlying the observed heavy rain event and the model's capability to predict, in hindcast mode, its structure and evolution. The impact of forecast initialization and of model vertical discretization on hindcast results is also examined. Comparison between model hindcasts and observed fields provided by raingauge data, satellite data, and radar data show that this particular event is strongly sensitive to the details of the mesoscale initialization despite being evolved from a relatively large scale weather system. Only meso-γ details of the event were not well captured by the best setting of the ARW-WRF model and so peak hourly rainfalls were not exceptionally well reproduced. The results also show that specification of microphysical parameters suitable to these events have a positive impact on the prediction of heavy precipitation intensity values.
•Extreme rainfall event in Genoa city on 4 November 2011 generated flash floods that killed six people.•Explicit convection improves the quantity and spatial distribution of precipitation field.•Maritime value in the autoconversion initial drop size concentration improves the model forecasts.
Bioaerosols are relevant for public health and may play an important role in the climate system, but their atmospheric abundance, properties, and sources are not well understood. Here we show that ...the concentration of airborne biological particles in a North American forest ecosystem increases significantly during rain and that bioparticles are closely correlated with atmospheric ice nuclei (IN). The greatest increase of bioparticles and IN occurred in the size range of 2–6 μm, which is characteristic for bacterial aggregates and fungal spores. By DNA analysis we found high diversities of airborne bacteria and fungi, including groups containing human and plant pathogens (mildew, smut and rust fungi, molds, Enterobacteriaceae, Pseudomonadaceae). In addition to detecting known bacterial and fungal IN (Pseudomonas sp., Fusarium sporotrichioides), we discovered two species of IN-active fungi that were not previously known as biological ice nucleators (Isaria farinosa and Acremonium implicatum). Our findings suggest that atmospheric bioaerosols, IN, and rainfall are more tightly coupled than previously assumed.
A North American epidemic of mountain pine beetle (MPB) has disturbed over 5 million ha of forest containing headwater catchments crucial to water resources. However, there are limited observations ...of MPB effects on partitioning of precipitation between vapor loss and streamflow, and to our knowledge these fluxes have not been observed simultaneously following disturbance. We combined eddy covariance vapor loss (V), catchment streamflow (Q), and stable isotope indicators of evaporation (E) to quantify hydrologic partitioning over 3 years in MPB‐impacted and control sites. Annual control V was conservative, varying only from 573 to 623 mm, while MPB site V varied more widely from 570 to 700 mm. During wet periods, MPB site V was greater than control V in spite of similar above‐canopy potential evapotranspiration (PET). During a wet year, annual MPB V was greater and annual Q was lower as compared to an average year, while in a dry year, essentially all water was partitioned to V. Ratios of 2H and 18O in stream and soil water showed no kinetic evaporation at the control site, while MPB isotope ratios fell below the local meteoric water line, indicating greater E and snowpack sublimation (Ss) counteracted reductions in transpiration (T) and sublimation of canopy‐intercepted snow (Sc). Increased E was possibly driven by reduced canopy shading of shortwave radiation, which averaged 21 W m−2 during summer under control forest as compared to 66 W m−2 under MPB forest. These results show that abiotic vapor losses may limit widely expected streamflow increases.
Key Points
Water vapor loss remained high following forest mortality
Abiotic evaporation counteracted reduced transpiration
Streamflow did not increase, in contrast to expectations
Hillslope‐scale rainfall‐runoff processes leading to a fast catchment response are not explicitly included in land surface models (LSMs) for use in earth system models (ESMs) due to computational ...constraints. This study presents a hybrid‐3D hillslope hydrological model (h3D) that couples a 1‐D vertical soil column model with a lateral pseudo‐2D saturated zone and overland flow model for use in ESMs. By representing vertical and lateral responses separately at different spatial resolutions, h3D is computationally efficient. The h3D model was first tested for three different hillslope planforms (uniform, convergent and divergent). We then compared h3D (with single and multiple soil columns) with a complex physically based 3‐D model and a simple 1‐D soil moisture model coupled with an unconfined aquifer (as typically used in LSMs). It is found that simulations obtained by the simple 1‐D model vary considerably from the complex 3‐D model and are not able to represent hillslope‐scale variations in the lateral flow response. In contrast, the single soil column h3D model shows a much better performance and saves computational time by 2‐3 orders of magnitude compared with the complex 3‐D model. When multiple vertical soil columns are implemented, the resulting hydrological responses (soil moisture, water table depth, and base flow along the hillslope) from h3D are nearly identical to those predicted by the complex 3‐D model, but still saves computational time. As such, the computational efficiency of the h3D model provides a valuable and promising approach to incorporating hillslope‐scale hydrological processes into continental and global‐scale ESMs.
Key Points:
This study presents a hybrid‐3D model for the hillslope hydrological response
Hydrological simulations are similar to those predicted by a 3‐D Richards model
The hybrid‐3D model is computationally 2‐3 orders of magnitude more efficient
The North American Monsoon (NAM) system controls the warm season climate over much of southwestern North America. In this semi-arid environment, understanding the regional behavior of the ...hydroclimatology and its associated modes of variability is critically important to effectively predicting and managing perpetually stressed regional water resources. Equally as important is understanding the relationships through which warm season precipitation is converted into streamflow. This work explores the hydroclimatology of northwestern Mexico, i.e. the core region of the NAM, by (a) presenting a thorough review of recent hydroclimatic investigations from the region and (b) developing a detailed hydroclimatology of 15, unregulated, headwater basins along the Sierra Madre Occidental mountains in western Mexico. The present work is distinct from previous studies as it focuses on the intra-seasonal evolution of rainfall-runoff relationships, and contrasts the sub-regional behavior of the rainfall-runoff response. It is found that there is substantial sub-regional coherence in the hydrological response to monsoon precipitation. Three physically plausible regions emerge from a rotated Principal Components Analysis of streamflow and basin-averaged precipitation. Month-to-month streamflow persistence, rainfall-runoff correlation scores and runoff coefficient values demonstrate regional coherence and are generally consistent with what is currently known about sub-regional aspects of NAM precipitation character.
Hillslopes are important for converting rainfall into runoff, influencing the terrestrial dynamics of the Earth's climate system. Recently, we developed a hybrid‐3‐D (h3D) hillslope hydrological ...model that gives similar results as a full 3‐D hydrological model but is up to 2–3 orders of magnitude faster computationally. Here h3D is assessed using a number of recharge‐drainage experiments within the Landscape Evolution Observatory (LEO) with accurate and high‐resolution (both temporally and spatially) observations of the inputs, outputs, and storage dynamics of several hillslopes. Such detailed measurements are generally not available for real‐world hillslopes. Results show that the h3D model captures the observed storage, base flow, and overland flow dynamics of both the larger LEO and the smaller miniLEO hillslopes very well. Sensitivity tests are also performed to understand h3Ds difficulty in representing the height of the saturated zone close to the seepage face of the miniLEO hillslope. Results reveal that a temporally constant parameters set is able to simulate the response of the miniLEO for each individual event. However, when one focuses on the saturated zone dynamics at 0.15 m from the seepage face, a stepwise evolution of the optimal model parameter for the saturated lateral conductivity parameter of the gravel layer occurs. This evolution might be related to the migration of soil particles within the hillslope. However, it is currently unclear whether and where this takes place (in the seepage face or within the parts of the loamy sand soil).
Key Points:
In this study, the h3D hillslope model is tested using Biosphere 2 LEO observations
The h3D model captures observed hillslope flow and storage dynamics very well
Results reveal the possibility of migrating soil particles close to the seepage face
This paper documents the sensitivity of the modeled evolution of the North American monsoon system (NAMS) to convective parameterization in terms of thermodynamic and circulation characteristics, ...stability profiles, and precipitation. The convective parameterization schemes (CPSs) of Betts-Miller-Janjic, Kain-Fritsch, and Grell were tested using version 3.4 of the PSU-NCAR fifth-generation Mesoscale Model (MM5) running in a pseudoclimate mode. Model results for the initial phase of the 1999 NAM are compared with surface climate station observations and seven radiosonde sites in Mexico and the southwestern United States. The results show substantial differences in modeled precipitation, surface climate, and atmospheric stability occuring between the different model simulations, which are attributable to the representation of convection in the model. Moreover, large intersimulation differences in the low-level circulation fields are found. While none of the CPSs tested gave perfect simulation of observations everywhere in the model domain, the Kain-Fritsch scheme generally gave significantly superior estimates of surface and upper air verification error statistics. (Author)
This paper explores the existence and potential causes of a stationary spatial anomaly, or pattern incoherence, in the seasonal distribution of warm season rainfall in western Mexico. The anomaly is ...evident in maps of the Month of Maximum Precipitation (MMP) variability over northwest Mexico (NWMx). Instead of occurring progressively as latitude increases, the MMP occurs in July in the southern part of western Mexico and along the main axis of the Sierra Madre Occidental (SMO) to the north, and in August in the central portion of the region, in Nayarit, Durango and Zacatecas. The Month of Maximum Streamflow (MMQ) occurs in a similar spatial pattern but shifts one month later. This feature is explored through inspection of the daily rainfall climatology of the region for stations with more than 20 years of data between 1940 and 2004. We hypothesize that this anomalous pattern in rainfall (and subsequent streamflow) is likely influenced by the complex thermodynamic interaction between the orography of the SMO and the regional monsoon circulation. The possibility that the canyon system known as the San Pedro Mezquital helps drive the anomalous increase of rainfall in August across latitudes limited to of Nayarit is explored. The correlation between rains that fall over watersheds on the western slope of the SMO and rainfall over the Mexican Plateau is also discussed. We also explore the relationship of the rainfall anomaly to the seasonal march of the Western Hemisphere Warm Pool (WHWP) and near shore Sea Surface Temperature (SST) variations as they may impact the land–sea thermal contrast. The results of this study based on daily rainfall and streamflow climatologies suggest that a region exists in Nayarit where atmosphere–ocean–land surface interactions lead to a relative phase-shift in the maximum precipitation and streamflow.
Analyses of rainfall characteristics and their linkage to physiographic features are made from the North American monsoon experiment (NAME) Event Rain Gauge Network (NERN) in northwest Mexico. The ...findings are based on the network configuration for the 2002 and 2003 warm seasons. Despite the relatively short record used, a clearer structure of core-region monsoon rainfall is beginning to emerge. In agreement with earlier, coarser-scale studies, the seasonal precipitation maximum overlies the western slope of the Sierra Madre Occidental but does not strictly parallel a particular elevation band. It is shown that the distance to the Gulf of California and, potentially, the configuration of the terrain profile may also play an important role in determining where the axis of maximum precipitation lies. The diurnal cycles of precipitation frequency and intensity are shown to have distinct relationships to terrain elevation that are qualitatively similar to those observed over the Front Range of the Rocky Mountains in the central-western United States. The relationship between precipitation and gulf surge events occurring during the summer of 2003 is also explored.
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